The present invention relates to a dental ultrasound instrument and more particularly an instrument for treating the periodontal pockets which are characteristic of an infection of the periodontium.
In effect, it is known that, although tartar is not a pathogenic product per se, it nonetheless constitutes, by reason of its alveolar porous constitution, a support capable of receiving and promoting the development of microbial fauna.
When tartar is deposited on the supergingival part of the tooth, viz. on the enamel thereof, it may easily be removed with the aid of a manual instrument or an ultrasound instrument moved.
The same does not apply when it is deposited on the subgingival part of the tooth, namely on the cementum thereof, due to the considerable roughness of the latter. In the latter case, the subgingival tartar will promote the formation of dental plaque which in the long run will lead to a disease of the periodontium, or periodontitis, which manifests itself by the presence of the periodontal pocket mentioned above. In the absence of treatment, periodontitis will lead to a loss of the attachment of the tooth and to a resorption of the alveolar bone. It is therefore essential to treat the periodontal pocket.
The purpose of the treatment which is carried out is conventionally to clean the surface of the root of the tooth in order to eliminate the harmful deposits therefrom, and then to polish it in order to obtain a smooth surface. Such an operation, called radicular surfacing, is effected "blind" for periodontal pockets of small dimensions. In the contrary case, a gingival flap is made, which allows direct access to the radicular surfaces affected by the disease.
Blind radicular surfacing requires particularly adapted instrumentation due, on the one hand, to the anatomical variety of the sites concerned and their difficult access and, on the other hand, due to the fragility of the tissues encountered. Certain of the instruments used to that end are of diverse forms and are used either in traction or in thrust. Among the instruments used in traction, the instruments of type "Crane Kaplan No. 6", "Goldman Fox No. 1" or "Mac Call" will be retained in particular. Certain instruments of the type operating in thrust are constituted by chisels presenting a straight, flat and bevelled cutting edge and a continuous blade (Zerfin 6 chisel).
All these instruments comprise contusive zones in order to allow engagement on the tartar which, due to the rough nature of the cementum, forms part thereof.
Among the instruments most used for radicular surfacing operations, curettes will be retained, and in particular so-called "Gracey" curettes which, by reason of their semi-circular cross-section, may be easily inserted in the majority of the zones of the dentition in order to effect both the scraping operation with their sharp zone and the polishing operation with their rounded zone. This type of instrument presents the drawback of requiring numerous periodic sharpenings. Moreover, when the contusive part of the blade encounters a piece of tartar, it is necessary to apply a high force to the instrument, which may prove dangerous for the surrounding tissues.
Furthermore, the time necessary for carrying out manual treatment by means of the above-mentioned instruments may prove to be very long and it is for this reason that it has been proposed to render this operational technique mechanical by activating these instruments by means of ultrasound generator devices, as proposed in particular in a Canadian Patent No. 597 313.
Another drawback of the instruments mentioned hereinabove is that, in order to effect an operation of radicular surfacing on the same tooth, the practitioner is obliged to change instruments several times during operation, which constitutes both a hindrance and a loss of time for him.
Although the ultrasound instruments avoid the practitioner tiring greatly and allow him to save considerable time, they nonetheless present a certain number of drawbacks which are essentially due to the fact that the instruments of this type do not take into account the most recent scientific data on the subject.
In effect, it is known that the operation of radicular surfacing mentioned hereinabove consists in removing the cementum and the dentine from the diseased places in order to eliminate those parts thereof containing microbial fauna. Unfortunately, this operation also has the effect of inducing phenomena of hypersensitivity or of ascending pulpitis and of subsequently promoting the adhesion of bacteria on the places thus treated.
At the present time, the so-called operations of debridement of the periodontal pocket seem to be preferred to the operation of radicular surfacing. Such an operation, unlike the latter one, respects the whole of the cementum and the dentine.
It consists in opening the periodontal pocket, cleaning the root and in effecting mechanical excision of the irritants of the dental and radicular surface. Debridement goes as far as the adjacent non-pathological tissues, upsets the microbial organization established, resulting in a non-inflammatory state of the tissues. Debridement makes it possible to achieve a total scarring of the lesion by detoxification of the tissues and cemento-genesis.
Such an operation requires a non-contusive instrument for effecting cleaning and smoothing both rapidly and non-aggressively, contrary to the effect of scraping/polishing obtained with conventional instruments, including those animated by ultrasounds.
Furthermore, it is known that ultrasound instruments used in dentistry are capable of producing an effect of cavitation which is advantageously used for eliminating the tartar which is deposited on the supergingival surfaces of the tooth. The instruments of the prior state of the art, which were described hereinabove, prove to be incapable, by the sole effect of cavitation that they create, of eliminating from the root of the tooth the subgingival concretions which adhere thereto. This is why these instruments present a contusive part whose effects are intended to be added to that of cavitation in order to "machine" to some extent the concretions to be eliminated.